title: Bandwidth-narrowed Bragg gratings inscribed in double-cladding fiber by femtosecond laser.
abstract: Bragg gratings with the bandwidth(FWHM) narrowed up to 79 pm were inscribed in double-cladding fiber with femtosecond radiation and a phase mask followed by an annealing treatment. With the annealing temperature below a critical value, the bandwidth of Bragg gratings induced by Type I-IR and Type II-IR index change was narrowed without the reduction of reflectivity. The bandwidth narrowing is due to the profile transformation of the refractive index modulation caused by the annealing treatment. This mechanism was verified by comparing bandwidth narrowing processes of FBGs written with different power densities.
authors.affiliation: Wuhan National Laboratory for Optoelectronics, Huazhong University of Science & Technology, Wuhan 430074, China.
authors.forename: Jiawei
authors.initials: J
authors.lastname: Shi
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Li
authors.forename: Shuhui
authors.initials: S
authors.lastname: Liu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Wang
authors.forename: Ningliang
authors.initials: N
authors.lastname: Liu
authors.forename: Peixiang
authors.initials: P
authors.lastname: Lu
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007834:Lasers; D012031:Refractometry / Q000295:instrumentation*